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High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4$

We report the magnetic phase diagram of single-crystalline LiFePO4 in magnetic fields up to 58 T and present a detailed study of magnetoelastic coupling by means of high-resolution capacitance dilatometry. Large anomalies at TN in the thermal-expansion coefficient α imply pronounced magnetoelastic c...

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Bibliographic Details
Main Authors: Werner, Johannes (Author) , Sauerland, Sven (Author) , Koo, Changhyun (Author) , Neef, Christoph (Author) , Pollithy, Anna (Author) , Klingeler, Rüdiger (Author)
Format: Article (Journal)
Language:English
Published: 24 June 2019
In: Physical review
Year: 2019, Volume: 99, Issue: 21
ISSN:2469-9969
DOI:10.1103/PhysRevB.99.214432
Online Access:Verlag, Volltext: https://doi.org/10.1103/PhysRevB.99.214432
Verlag, Volltext: https://link.aps.org/doi/10.1103/PhysRevB.99.214432
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Author Notes:J. Werner, S. Sauerland, C. Koo, C. Neef, A. Pollithy, Y. Skourski, and R. Klingeler
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Summary:We report the magnetic phase diagram of single-crystalline LiFePO4 in magnetic fields up to 58 T and present a detailed study of magnetoelastic coupling by means of high-resolution capacitance dilatometry. Large anomalies at TN in the thermal-expansion coefficient α imply pronounced magnetoelastic coupling. Quantitative analysis yields the magnetic Grüneisen parameter γmag=6.7(5)×10−7 mol/J. The positive hydrostatic pressure dependence dTN/dp=1.46(11) K/GPa is dominated by uniaxial effects along the a axis. Failure of Grüneisen scaling below ≈40K, i.e., below the peak temperature in the magnetoelectric coupling coefficient [7], implies several competing degrees of freedom. A broad and strongly magnetic field dependent anomaly in α in this temperature regime highlights the relevance of structure changes. Upon application of the magnetic field B||b axis, a pronounced jump in the magnetization implies spin reorientation at BSF=32T as well as a precursing phase at 29 T and T=1.5K. In a two-sublattice mean-field model, the saturation field Bsat,b=64(2)T enables assessing the effective antiferromagnetic exchange interaction Jaf=2.68(5)meV as well as anisotropies Db=−0.53(4)meV and Dc=0.44(8)meV.
Item Description:Im Titel ist die Zahl "4" tiefgestellt
Gesehen am 06.08.2019
Physical Description:Online Resource
ISSN:2469-9969
DOI:10.1103/PhysRevB.99.214432

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